So-called oxidative dyes are used for permanent intense dyeings with appropriate fastness properties. Oxidative dyes usually include two components, one component usually containing oxidative dye precursors, so-called developer components and coupler components. The developer components form the actual coloring substances under the influence of oxidizing agents, in particular hydrogen peroxide, which are added to the first component shortly before application to the hair, or under the influence of atmospheric oxygen or with coupling to one or more coupler components. The developer components generally include primary aromatic amines with an additional free or substituted hydroxyl group or amino group in para- or ortho-position, also including diaminopyridine derivatives, heterocyclic hydrazones, 4-aminopyrazolone derivatives and 2,4,5,6-tetraaminopyrimidine and derivatives thereof. Suitable coupler components usually include m-phenylenediamine derivatives, naphthols, resorcinol and resorcinol derivatives, pyrazolones, m-aminophenols and substituted pyridine derivatives. The oxidative dyes have excellent and long-lasting dyeing results.
Conventional oxidative dyes have a more alkaline pH which is definitely above 9.0 and is adjusted with alkalizing agents such as alkanolamines, ammonia or inorganic bases to stabilize the dye precursors during storage and to accelerate the reaction during oxidative application. Ammonia in particular gives good dyeing results but also has disadvantages for the user due to its odor and potential for irritation of skin and mucous membranes. The alkalizing agent causes swelling of keratinic fibers so that the dye precursors can penetrate well into the hair. However, the damaging effect of the oxidizing agent on the hair structure is also increased by the alkaline pH.
Therefore, special efforts have been devoted to the development of high-performance oxidative dyes containing one or more substances that essentially have no oxidizing effect but can enhance the effect of the oxidizing agent, in order to reduce the concentration thereof, while at the same time manifesting results with regard to lightening and dyeing. Then the reduction in oxidizing agent concentration may be associated with reduced damage to hair.
Prior Art. The use of Quassia amara extracts in cosmetic compositions was already known. For example, JP 2003 081850 A, WO 2007/048985, U.S. Pat. No. 8,293,291 and US 20150056310 A1 describe the use of Quassia amara extracts as wrinkle-reducing active ingredients to reduce facial lines or to strengthen the extracellular matrix (ECM) of facial skin. DE 102013213027A1 discloses the use of Quassia amara extracts to improve hair structure and promote hair growth.